Persistent infection

My tank has now been running for approximately four months, and no new fish or plants have been added for about three months. The problem first appeared as a white looking area around the mouth of one of my sterbii Corys along with the disappearance of his barbels. I considered this to probably be due to fungal infection and treated with Waterlife Protozine, malachite green and copper sulphate, and this has cleared up.
Now I have noticed a white ball like growth on the mouth of two of my neons and small white areas on the tail fin.
As Protozin is said to be effective against white spot and fungus I have repeated the treatment. The tank water tests negative for ammonia and nitrites. The infection shows no sign of clearing so I have carried out a 15% water change and started another course of treatment.
I have taken a photo of the neon, any ideas of the illness or alternative treatment welcomed.

@Deanasue had a neon that had a similar infection and so have a couple of other members.

I’m not sure we ever figured out what it was? I believe @Colin_T gave some advice though.

It’s not viral or bacterial, at least not to the point of responding to meds. I’ve narrowed it down to one of 2 things. 1). They’ve gotten nipped and growth grew as a result 2) something genetic that occurs in some. I have about 50 neons in a tank right now. Have had them for 8 months and not one has had the growth start. They came from different places so odds are that if it were genetic, some of mine would have it. So we’re back to nipping. My tank is 55G with plenty of room so no aggression. Leads me to believe it is nipping and explains why always the mouth area. If they can eat, still schoaling with the others, and good coloring then I would just watch it. I had 2 that lived out their lives with it.

Thanks for your help guys, the fish are all eating and fully coloured. I will stop the medication and just keep a close watch on any developments.

The growth (white lump) on the mouth is not fungal, bacterial or protozoan.

It's not a genetic issue because it would show up on lots of young fish and it is only appearing on the odd adult fish.

I'm going to disagree with Deanasue and say it's viral. There are no treatments for viruses, certainly not in fish. It's just a matter of keeping the conditions good and feeding the fish a varied diet.

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As for the white marks on the tail, I need more pictures that are in focus to identify them. But stop adding chemicals.